Not Applicable.
Not Applicable.
1. Field of the Invention
The present invention relates generally to meters that measure the flow of a fluid. More particularly, the present invention relates to ultrasonic meters measuring fluid flow through a pipe. Still more particularly, the present invention relates to a structure for mounting transducers to an ultrasonic flow meter.
2. Description of the Related Art
After a hydrocarbon, such as natural gas, has been removed from the ground, it is often transported from place to place via pipelines. Very often, an owner or operator of a pipeline desires to accurately know how much gas is flowing through the pipeline. For example, where a billion standard cubic feet of natural gas flows through a single pipeline, even small percentage errors can result in serious miscalculations regarding the amount of gas flowing through the pipeline. Further, particular accuracy for the measurement is demanded when gas is changing hands, or xe2x80x9ccustodyxe2x80x9d, because custody transfer applications often involve the exchange of money. Even so, an accurate meter is desirable for all phases of gas or fluid production, transportation, and distribution operations, and for off-shore platforms.
In response to the need for accurate gas flow measurement, ultrasonic flowmeters were developed. Ultrasonic flowmeters, also named sonic or acoustic flowmeters, revolutionized the gas industry because of their many advantages. For example, ultrasonic flowmeters are accurate over a large range of flow rates. Because ultrasonic gas flowmeters are non-intrusive, gas flows through the gas pipeline without encountering an increased pressure region. Consequently, considerable savings are achieved because the gas flows more easily in the pipe. In addition, ultrasonic flowmeters can also measure gas flow accurately despite changing gas composition.
FIG. 1 shows a prior art ultrasonic transducer mount 100. The mount 100 includes a base 130 with a side surface 131 and a flat surface 132. Arcuately located on the base flat surface 132 are cap screw holes 110-113 for receiving cap screws 114-117 (not shown) respectively. Also located on base flat surface 132 are two jackscrew holes 120, 121 located 180xc2x0 apart for receiving jackscrews (not shown). The jackscrews are used for removal of the mount from the meter housing. Also located on the base flat surface 132 are two mount cover holes 118, 119 located 180xc2x0 apart for receiving the mount cover screws (not shown). Extending from the base 130 is a holder sleeve 140. The inner diameter (ID) of the holder sleeve 140 engages a transducer holder that holds a transducer (not shown). On the outside of holder sleeve 140 is union sleeve 150. Sleeve 150 is not removable from holder sleeve 140. On the outer diameter (OD) of union sleeve 150 are threads 151 for engagement with a union nut (not shown). The union nut is part of an extractor tool (not shown) for removal of the transducer holder and transducer.
In operation, the cap screws (not shown) attach the mount 100 to a meter housing (not shown). The transducer and transducer holder are then inserted into the holder sleeve 140. Once inserted, the transducer holder forms a fluid-tight seal at the joint with the holder sleeve. A mount cover (not shown) attaches to the mount base with screws that engage the mount cover holes 118, 119. The mount cover locks the transducer holder in place and prevents inadvertent disassembly during use and electrical connection to the transducer.
For removal of the transducer holder and transducer, first the mount cover is removed. The extractor tool (not shown) is then attached to the transducer mount. The extractor tool consists of an extractor tool valve (not shown) and a removable unit for isolation of the transducer holder and transducer from the transducer mount and meter housing. The extractor tool attaches to the transducer mount by the extractor tool valve union nut (not shown) engaging the union sleeve threads 151. Once engaged, the extractor tool makes an fluid-tight seal with the union valve seal. This seal allows removal of the transducer holder and transducer without releasing pressure from the meter housing and pipeline. The transducer and transducer holder are then removed from the holder sleeve 140 through the extractor tool valve and placed in a chamber in the extractor tool removable unit. Once the transducer holder and transducer are removed, the chamber is sealed from the holder sleeve. Once sealed, the transducer and transducer holder can be removed from the extractor tool.
For removal of the transducer mount 100, pressure must be vented from the housing and the cap screws (not shown) must be removed. Jackscrews are then inserted into jackscrew holes 120, 121. As the screws draw into the holes, they engage the meter housing surface. Further drawing the screws into the jackscrew holes forces the mount 100 out of engagement with the meter housing.
The large size of the current T-slot transducer mount provides certain drawbacks. Specifically, the current transducer mount causes problems with small meter housings. For example, the cast bosses for the very large OD transducer mounts greatly increase the casting weight of the housing casting because of the material needed at each transducer location boss to allow the mount to be attached. The housing transducer location bosses for the very large OD mounts also greatly increase the end to end length of the meter housing. The increased length is a major concern because the bore of the meter must be machined. The ability to machine a small ID over a very long length becomes harder as the length increases. This is true even if the bore is machined from each end. There are also cost issues concerned with the large size transducer mounts because of the large amount of material used.
It would be advantageous to design a transducer mount that is smaller in size than conventional designs, and that can be manufactured more inexpensively. Ideally, the new transducer mount would be compatible with existing extractor tools, transducers, and holders to facilitate a smooth transition to the new mount design. The new transducer mount would also allow for a smaller size meter housing than conventional meter housings. The smaller size meter housing would have a decreased casting weight and a decreased end to end length. It would also be advantageous to locate the transducer ports in the housing in the same location for different pressure rating transducer mounts. Despite the apparent advantages of such a transducer mount, to date no such mount has been commercially introduced.
The present invention comprises an improved ultrasonic transducer mount. Unlike prior transducer mounts, the improved transducer mount includes a removable union sleeve with an outer diameter (OD) that engages the inner diameter (ID) of the extractor tool union nut. A retaining ring holds the union sleeve in place on the outside of a transducer holder sleeve. The union sleeve and the retaining ring need only be used with the extractor tool for removal of the transducer.
According to an exemplary embodiment, the union sleeve fits over a holder sleeve on the mount. The holder sleeve has at least one flat surface that engages a similar configuration on the ID of the union sleeve. The flat surface(s) prevent(s) relative rotation between the union sleeve and holder sleeve after installation on the mount and during engagement and disengagement of the extractor tool.
The end of the union sleeve contacting the retaining ring includes a counter bore on the contacting face. The counter bore fully circumscribes the retaining ring when the union nut pulls the union sleeve against the retaining ring during engagement. This counter bore prevents inadvertent disassembly of the retaining ring from the groove if the extractor tool valve rotates as the union nut engages. Inadvertent disassembly occurs because rotation of the extractor tool valve rotates the union seal of the valve assembly and this rotation may un-spiral the retaining ring from its groove.
The design of the union sleeve, the counter bore on the end of the union sleeve, retaining ring, retaining ring groove, and the placement of the retaining ring groove on the mount are designed so that when the union nut and union seal of the extractor tool valve engage the mount, the retaining ring is compressed by the surface on the bottom of the counter bore on the end of the union sleeve and the end of the union seal. The compression of the retaining ring prevents the retaining ring from becoming canted within the groove as the pressure and other forces pull on the extractor tool assembly. By keeping the retaining ring perpendicular to the OD in the groove, the strength of the retaining ring and groove are greatly increased and wear is minimized.
With a removable union sleeve, the mount base can be smaller in size. This is because less clearance is required around the union sleeve threads for the cap screws that attach the mount base to the meter housing. With the mount base smaller, the mount cover is too big for direct attachment. To attach the mount cover, two mount cover retaining brackets connect to the mount base and are located 180xc2x0 apart. The retaining brackets have screw holes for attachment of the mount cover by the mount cover screws. The retaining brackets also act as jackscrew holes eliminating the need for the holes on mount base. When the cover and mount base attachment means have been removed, the threaded holes in both of the retaining brackets receive the jackscrews. When the jackscrews tighten, the screws engage the meter housing and force the mount from the housing. The brackets thus also eliminate the need to provide additional holes solely for jackscrews.
Because the new design mount does not include a permanent OD surface for engagement with the extractor tool, the mount base can be made much smaller. The reduced mount size reduces cost by reducing the material needed. The reduced size also saves manufacturing costs with the ability to be investment cast. The smaller transducer mount also decreases the casting weight of the housing casting with the use of smaller housing transducer location bosses. The smaller transducer mount also decreases the end to end length of the small size meter housing. The smaller transducer mount also allows location of the transducer ports in the housing in the same location for different pressure rating transducer mounts. The smaller transducer mount, however, it still compatible with existing transducers and transducer holders.